Rotating multi-monolith bed movement system for removing CO2 from the atmosphere

ABSTRACT

A system for removing carbon dioxide from a carbon dioxide laden gas mixture, the system comprising two groups of carbon dioxide removal structures, each removal structure within each group comprising a porous solid mass substrate supported on the structure; and a sorbent that is capable of adsorbing or binding to carbon dioxide, to remove carbon dioxide from a gas mixture, the sorbent being supported upon the surfaces of the porous mass substrate solid; an endless loop support for each of the groups of the removal structures, the endless loop support being so arranged as to move the support structures of each group along a closed curve while being exposed to a stream of the gas mixture; and a sealable regeneration box at one location along each of the endless loop supports, in which, when a porous solid mass substrate is sealed in place therein, carbon dioxide adsorbed upon the sorbent is stripped from the sorbent and the sorbent regenerated; each removal structural supporting a porous substrate in a position to be exposed to a flow of carbon dioxide laden gas mixture so as to allow for the removal of CO 2  from the gas mixture; the number of removal structures to the number of regeneration boxes being directly determined by the ratio of the time to adsorb CO 2 , from a base level to desired level on the sorbent, to the time to strip the CO 2  from the desired level back to the base level.

This application is a divisional of U.S. application Ser. No. 14/587,716filed Dec. 31, 2014 and claims the benefit of priority pursuant to 35U.S.C. 119(e) from a U.S. Provisional Patent Application havingApplication No. 61/922,338 filed Dec. 31, 2013, the text of which isfully incorporated by reference herein as if repeated below.

BACKGROUND

The present invention relates to systems and methods for removinggreenhouse gases from the atmosphere, and in particular to systems andmethods for removing carbon dioxide from a stream of gas, includingambient air.

As a further improvement to the system described in copending U.S.application Ser. No. 13/098,370, filed on Apr. 29, 2011, a suitablesystem and process is presented that it is now recognized can beutilized for a broader range of use than disclosed in that earlierapplication, especially when further modified. The disclosure of thatcopending application is incorporated by reference herein as if repeatedin full, as modified by the new disclosure presented herein.

There is much attention currently focused on trying to achieve threesomewhat conflicting energy related objectives: 1) provide affordableenergy for economic development; 2) achieve energy security; and 3)avoid the destructive climate change caused by global warming. However,there is no feasible way to avoid using fossil fuels during the rest ofthis century if we are to have the energy needed for economic prosperityand avoid energy shortfalls that could lead to conflict.

It is mostly undisputed by scientists that an increase in the amount ofso-called greenhouse gases like carbon dioxide (methane and water vaporare the other major greenhouse gases) will increase the averagetemperature of the planet.

It is also clear that there is no solution that only reduces the ongoinghuman contributions to carbon dioxide emissions that can successfullyremove the risk of climate change. Removing additional CO₂ from theatmosphere is also necessary. With air extraction and the capability toincrease or decrease the amount of carbon dioxide in the atmosphere, onecan in principle compensate for other greenhouse gases like methane(both naturally occurring and from human activity) that can increasetheir concentrations and cause climate change.

Until the recent inventions by the present applicant, it was thegenerally accepted belief among experts in the field that it was noteconomically feasible to capture carbon dioxide directly from theatmosphere because of the low concentration of that compound, in orderto at least slow down the increase of so-called ‘greenhouse’ gases inthe atmosphere. It was subsequently shown by the copending, commonlyowned, prior applications that it was in fact practical and efficient tocarry out such CO₂ reductions under specified conditions.

It was shown that under ambient conditions CO₂ can be efficientlyextracted from the air, at ambient conditions, using a suitableregenerable sorbent system and a low temperature stripping orregeneration process, and that such a process can be expanded to removeCO₂.from mixtures of effluent gases mixed with a major amount of ambientair, so as to not only remove the CO₂ from flue gas but to removeadditional CO₂ from the atmosphere so as to achieve a net reduction inCO₂ in the atmosphere at lower cost and higher efficiency.

SUMMARY OF THE PRESENT INVENTION

The present invention provides further new and useful systems andmethods for removing carbon dioxide from a mass of carbon dioxide ladenair, at higher efficiencies and lower overall costs including lowercapital expenses (“CAPEX”) and lower operating expenses (“OPEX”).

In accordance with the present invention, a novel process and system hasbeen developed utilizing assemblies of a plurality of monoliths, orbeds, that are combined with a single regeneration box, in a ratiodependent upon the ratio of the speed of adsorption compared to thespeed of regeneration of the sorbent. In preferred embodiments, themonoliths are supported on a closed loop track, preferably forming aclosed curve; upon which the monoliths are rotated along the track, insuccession, while being exposed to a moving stream of ambient air or amixture of gases comprising a major proportion of ambient air. At onelocation along the track, the rotation is halted and one of themonoliths is moved into a sealed box for processing to strip CO₂ fromthe sorbent to regenerate the sorbent. When the sorbent is regenerated,the monoliths are rotated around the track until the next monolith is inposition to enter the regeneration box, when the rotation of all of themonoliths is next halted.

Each monolith is formed of a porous substrate having on its surfacescarbon dioxide adsorbing amine sites, preferably with a high proportionof primary amines. As the monoliths move along the track, they adsorbCO₂ from the moving gas streams until each monolith reaches the sealedbox. Once sealed within the box, the sorbent is treated to cause the CO₂to be stripped from the sorbent, regenerating the sorbent. The strippedCO₂ is removed from the box and captured. The monolith with theregenerated sorbent then moves out of the sealed box and moves along thetrack with the other monolith to adsorb more CO₂, until the nextmonolith is rotated into position to be moved into the regeneration box.At the stripping/regeneration location, the monolith can be moved into abox located above or below the grade of the track, or the box can belocated so that the monolith moves into the box at the same grade levelas the track, forming a seal with the monolith. These severalalternatives are further defined below and diagrammed in theaccompanying drawings.

In the instances where the regeneration box is below or above grade, thesystem must include a sub-system for raising or lowering the monolith.In systems where the regeneration box is on grade with the tracks, amore complex sealing arrangement will be required, for providing a sealalong the sides as well as along the top and/or bottom surfaces.

CO₂ Adsorption and Removal Process

The basic premise of this process is that CO₂ is adsorbed from theatmosphere by passing air or a mixture of air and effluent gas, througha sorbent bed, preferably at or close to ambient conditions. Once theCO₂ has been adsorbed by the sorbent, the CO₂ has to be collected, andthe sorbent regenerated. The latter step is performed by heating thesorbent with steam in the sealed containment box to release the CO₂ andregenerate the sorbent. The CO₂ is collected from the box, and thesorbent is then available to re-adsorb CO₂ from the atmosphere. The onlyprimary limitation on the process is that the sorbent can bede-activated if exposed to air if it is at a “too high” temperature.Thus the sorbent may have to be cooled before the monolith leaves thebox and is returned to the air stream.

Generally, a longer time is required for adsorption of CO₂ from ambientair than for the release of the CO₂ in the regeneration step. With thecurrent generation of sorbent this difference will require an adsorptionperiod approximately ten times greater for the adsorption step comparedwith that required for CO₂ release and sorbent regeneration, whentreating ambient air. Thus a system with ten monoliths and a singleregeneration unit has been adopted as the current basis for anindividual rotating system. If the performance of the sorbent isimproved over time, this ratio of adsorption time to desorption time,and thus the number of monoliths, required in a system, should bereduced. In particular, if a higher loading embodiment of the sorbent isused a one hour adsorption time would be viable, thus requiring oneregeneration box to serve only five monoliths. In addition the relativetreatment times will vary with the concentration of CO₂ in the gasmixture treated, such that the higher the CO₂ content, the shorter theadsorption time relative to the regeneration time, e.g., by mixing acombustion effluent (“flue gas”) with the ambient air through a gasmixer.

The chemical and physical activity within the monoliths, both during theadsorption cycle and the regeneration cycle in the sealed box, issubstantially the same as is described in prior copending applicationSer. Nos. 13/886,207 and 13/925,679. The disclosures of those copendingapplications are incorporated by reference herein as if repeated infull, as modified by the new disclosure presented herein. In the systemaccording to the present invention, each rotating system provides onesealable regeneration box for each group of rotating monoliths, thenumber of monoliths being dependent upon the relative times to achievethe desired adsorption and the desired regeneration. In addition, it hasbeen found that greater efficiencies and lower costs are achieved byspatially relating and temporally operating two of the rotating systemsin a suitable relationship to allow the regeneration boxes for the tworotating monolith systems to interact, such that each is preheated bythe remaining heat in the other as a result of regeneration in theother; this also efficiently cools down the regenerated monolith beforeit is returned to its adsorption cycle on the rotating track.

This interaction between the regeneration boxes is achieved inaccordance with this invention, by lowering the pressure of the firstbox system so that the steam and water remaining in the first boxevaporate after the release of CO₂, and the system cools to thesaturation temperature of the steam at its lowered partial pressure.Furthermore, as described below, the heat released in this process isused to pre-heat the second sorbent bed and thus provides approximately50% sensible heat recovery, with a beneficial impact on energy and wateruse. This concept can be used even if an oxygen resistant sorbent isutilized. The sensitivity of the sorbent to oxygen de-activation athigher temperatures is being addressed during the development processand it is anticipated that its performance will be improved over time.

As discussed above, the sorbent bed is preferably cooled before it isexposed to air so as to avoid de-activation by the oxygen in the air.This cooling is achieved by lowering the system pressure and thuslowering the steam saturation temperature. This has been shown to beeffective in eliminating the sorbent deactivation issue as it lowers thetemperature of the system. There is thus a significant amount of energyremoved from the bed that is cooled during the de-pressurization step. Afresh bed that has finished its CO₂ adsorption step has to be heated torelease the CO₂ and regenerate the sorbent. This heat could be providedsolely by the atmospheric pressure steam, but this is an additionaloperating cost. In order to minimize this operating cost, a two-beddesign concept has been developed. In this concept the heat that isremoved from the box that is being cooled by reducing the systempressure, and thus the steam saturation temperature, is used topartially pre-heat a second box containing a bed that has finishedadsorbing CO₂ from the air and which is to be heated to start the CO₂removal and sorbent regeneration step. Thus the steam usage is reducedby using heat from the cooling of the first box to increase thetemperature of the second box. The remaining heat duty for the secondbox is achieved by adding steam, preferably at atmospheric pressure.This process is repeated for the other rotating monoliths in each of thetwo boxes and improves the thermal efficiency of the system.

These and other features of this invention are described in, or areapparent from, the following detailed description, and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES AND EXHIBITS

FIG. 1 is a diagrammatic top view of a mutually interactive pair ofrotating multi-monolith systems for removing carbon dioxide from theatmosphere according to an exemplary embodiment of this invention;

FIG. 2 is a diagrammatic elevation view of the rotating multi-monolithsystem of FIG. 1 for removing carbon dioxide from the atmosphereaccording to an exemplary embodiment of this invention;

FIG. 3 is a diagrammatic top view of an alternative mutually interactivepair of rotating multi-monolith systems for removing carbon dioxide fromthe atmosphere according to another exemplary embodiment of thisinvention;

FIG. 4 is a diagrammatic elevation view of the rotating multi-monolithsystem of FIG. 3 for removing carbon dioxide from the atmosphereaccording to that exemplary embodiment of this invention;

FIGS. 5 and 5A-H are schematic illustrations of a vertical offsetversion of a pair of regenerating chambers for removing carbon dioxidefrom the monolith medium of FIGS. 1 through 4, utilizing a verticalmotion system or elevator to move the monolith between the rotatingtrack level, upper air contact position (where the air movement is aidedby a mechanical blower) and the vertically offset regeneration chamberposition;

FIG. 6 is a top plan [schematic elevation] view of the regenerationchambers and monoliths on adjacent monolith systems showing the pipingsystem arrangement for each chamber and between the chambers;

FIGS. 7A and B are schematic elevation views showing fans which arestationary and which rotate with each monolith, respectively;

FIG. 8A is a diagrammatic side elevation view of a Design for DualInduced Axial Fans and Plenums of FIGS. 7A, B;

FIG. 8B is a diagrammatic front elevation view of a Design for DualInduced Axial Fans and Plenums of FIGS. 7A, B;

FIG. 9 is a diagrammatic cut-away elevation view of the Design for DualInduced Axial Fans and Plenums of FIG. 8B, along lines 9-9;

FIGS. 10A, 10B and 10C depict the Design of Seal Systems on themonoliths, depending on the location of the regeneration position, wherethe Angles and Dimensions are Exaggerated for Explanation Purposes;

FIG. 11 is a diagrammatic top view of a mutually interactive pair ofrotating multi-monolith systems for removing carbon dioxide from theatmosphere according to another exemplary embodiment of this invention;and

FIG. 12 is a diagrammatic elevation view of the mutually interactivepair of rotating multi-monolith system, taken along lines 11-11 of FIG.11, for removing carbon dioxide from the atmosphere.

DETAILED DESCRIPTION OF INVENTION

A conceptual design for a system to perform these operations is shown inFIGS. 1 and 2. A slight variation on the concept is shown in FIGS. 3 and4. The overall conceptual design is discussed above, and a detaileddiscussion of the operation and the ancillary equipment that will berequired is set out below.

In this embodiment, there are ten “monoliths” located in a decagonarrangement and which are located on a circular track. There are twocircular/decagon assemblies associated with each process unit and theyinteract with each other (see FIGS. 1-4). Air is passed through themonoliths by induced draft fans located on the inner sides of themonoliths. At one location the monoliths are in a position adjacent to asingle sealable chamber box, into which each monolith is inserted, asshown by vertically moving the bed out from the track, for processing(i.e. where they are heated to a temperature of not greater than 130 C.,and more preferably not above 120 C., preferably with precise heat steamto release the CO₂ from the sorbent and regenerate the sorbent).Alternatively, the box can be on grade. In this embodiment, theadsorption time for adsorbing CO₂ by the monolith is ten times as longas sorbent regeneration time.

It should be understood that although the use of porous monoliths ispreferred, it is feasible to use stationary beds of porous particulate,or granular, material supported within a frame, in place of themonolith. In both cases the porous substrate supports an amine sorbentfor CO₂, when the bed has the same surface area as the monolith forsupporting the adsorbent.

Mechanical Requirements

FIGS. 1-4, 11 and 12 show the basic operational concepts of the system.There are ten “monoliths” 21, 22 located in each decagon assemblyarrangement and which are movably supported on a circular track 31, 33.There are two circular/decagon assemblies A, B associated with eachprocess unit and they interact with each other. Air is passed througheach of the monoliths 21, 22 by induced draft fans 23, 26, locatedradially interiorly of each of the decagon assemblies, and inducing aflow of air out of the inner circumferential surface of each monolith,and up away from the system. At one location along the track 31, 33, themonoliths 21, 22 are adjacent to a sealable regeneration box 25, 27 intowhich the monoliths 22, 22 are inserted for regeneration processingafter having completed one rotation around the track.

Thus, as shown in FIGS. 1 and 2, a first Bed 21 is rotated into positionbeneath the regeneration box 25 and then moved vertically upwardly intothe box 25 for processing; or if the box 27 is located below grade, FIG.4, the Beal 22, is then moved vertically downwardly into the box 127 forprocessing; or if on grade, assembly is rotated to move the Bed 21, 22out of the box 27, so that Bed 21, 22 is in position when movement alongthe track is halted for all of the monoliths. When the Bed 21 has beenregenerated it is moved back onto the track and the bed assembly isrotated, so that the next Bed 21-2, 22-2 is in position. Bed 2 is thenmoved into the box for processing and then returned to the ring. Thisprocess is repeated continually. The two ring assemblies operatetogether, although the monoliths for each decagon are moved in and outof their boxes at slightly different times, as explained below, to allowfor the passage of heat, e.g., between Box 25 and Box 27, whenregeneration in one is completed to provide for preheating of the otherbox. This saves heat at the beginning of the regeneration and reducescost of cooling the bed after regeneration.

Three locations for the regeneration boxes 25, 27 are presented. InFIGS. 1 and 2, the regeneration boxes 25, 27 are placed above therotating bed assemblies (at nominal grade) and the monoliths are movedvertically up into the boxes for regeneration. The only elevatedstructure is that required for the boxes, which are located above therotating monoliths on a cantilevered structure.

In FIGS. 3 and 4 the boxes 125, 127 are located below grade and underthe rotating bed assemblies. The boxes would be located in a singleexcavation with adequate access for maintenance and process piping. Thebeds are moved vertically downwardly into the boxes.

In FIGS. 11 and 12 the regeneration boxes 321, 327 are located on gradewith the rotating bed assemblies. The boxes would be located withadequate access for maintenance and process piping also on grade.Suitable mutually sealing surfaces would be located on the box and oneach bed, so that as the bed rotates into position in the box, the box322, 327 is sealed.

In all cases ancillary equipment (such as pumps, control systems, etc.)would preferably be located at grade within the circumference of thetrack supporting the rotating bed assemblies 29, 39. The regenerationboxes could be located in different levels, in particular situationswithout departing from the concept of this invention.

These designs, compared to prior disclosed apparatus in the prior art,would:

-   -   Minimize structural steel;    -   Place all major equipment at grade level apart from the        regeneration boxes which are only acting as containment vessels;    -   Ensure that there is no interference with air flow to the        monoliths, where the boxes are at different levels from the        track;    -   Only require one or no vertical movement equipment for the        monoliths, for insertion into the single box for each group of,        e.g., 10, monoliths;    -   Minimize or eliminate the time required for bed movements in and        out of box, especially when the boxes are on grade,    -   Allow all piping to be in fixed positions; and    -   Allow the two regeneration boxes to be adjacent to each other        with minimum clearance to permit the heat exchange desirable for        increased efficiency.

The mechanical operations, with necessary machinery and power, that arerequired include:

-   -   Rotation of the two sets of bed assemblies around a circular        track on a support structure    -   Precise locating elements to precisely locate the position where        the monoliths are to be stopped so as to ensure the free        movement of the monoliths into and out of the regeneration box    -   Removal of the bed from the bed assembly on the track, insertion        of the bed into the regeneration box, removal of the bed from        the regeneration box and re-insertion of the bed into its        position on the track assembly. All of these movements occurring        in a vertical direction, or alternatively as part of the        horizontal rotational movement on the track. The monoliths and        regeneration boxes are designed so that, for vertically movable        monoliths there is an air-tight seal between the top or bottom        of each monolith and the support structure of the box. Examples        of some conceptual designs for such seals are shown in FIG. 10.

In all cases, referring to FIGS. 1-6, a Bed 21-1 (Ring A) is rotatedinto position and then moved up or downwardly into the Box 25 forprocessing. The pressure in Box 25 (containing Bed 21-1, Ring A) isreduced using, e.g., a vacuum pump 230, to less than 0.2 BarA. The Box25 is heated with steam at atmospheric pressure through line 235 and CO₂is generated from Bed 21-1 and removed through the outlet piping 237from the Box 25 for the CO₂ and condensate which is separated on acondenser 240 (FIG. 5A). Bed 22-1 (Ring B) is then placed in Box 27(Ring B) while Box 25 is being processed, as above (FIG. 5B). The steamsupply to Box 25 is stopped and the outlet piping for the CO₂ andcondensate isolated. Box 25 and Box 27 are connected by opening valve126 in connecting piping 125 (FIG. 5C).

The pressure in Box 27 is lowered using a vacuum pump 330 associatedwith Box 27. This lowers the system pressure in both boxes and draws thesteam and inerts remaining in Box 25 through Box 27 and then to thevacuum pump. This cools Box 25 (and thus Bed 21-1 Ring A) to a lowertemperature (i.e. the saturation temperature at the partial pressure ofthe steam in the box) and reduces the potential for oxygen deactivationof the sorbent when the Bed 21-1 is placed back in the air stream. Thisprocess also pre-heats Box 27 (and thus Bed 22-1 Ring B) from ambienttemperature up to the saturation temperature at the partial pressure ofthe steam in the box 250. Thus energy has been recovered and the amountof atmospheric pressure steam required to heat the second Box 27 (andBed 22-1 Ring B) is reduced (FIG. 5D). As the vacuum pump 330 lowerspressure in the Boxes 25 and 27, the first Box 25 is reduced intemperature (from 100° C. approx. to some intermediate temperature) andthe second Box 27 is increased in temperature (from ambient to the sameintermediate temperature). CO₂ and inerts are removed from the system bythe vacuum pump 330.

The valve between the first Box 25 and the second Box 27 is closed andthe boxes isolated from each other. Bed 21-1 Ring A is now cooled belowthe temperature where oxygen deactivation of the sorbent is of concernwhen the bed is placed back in the air stream. The second Box 27 and Bed22-1, Ring B, have been preheated and thus the amount of steam requiredfor heating the Box and Bed is reduced (FIG. 5E). Bed 21-1 Ring A isthen raised back into the bed assembly. The Ring A bed assembly isrotated by one bed and Bed 21-2 Ring A is then inserted into Box 25,where it is ready for preheating. Box 27 is heated with atmosphericsteam and the stripped CO₂ is collected (FIG. 5F).

When the second Box 27 (containing Bed 22-1 Ring B) has been fullyregenerated the steam supply to Box B is isolated and the piping for theCO₂ and condensate is isolated using valves 241, 242. The valving 126between the first Box 25 and the second Box 27 is opened and thepressure in the Boxes 25, 27 is reduced using the vacuum pump 230 systemfor Box 25. The temperature of the second Box 27 (and thus Bed 22-1,Ring B) is reduced (see 5 above). The temperature of the first Box 25(containing Bed 21-2, Ring A) is increased (see 5 above) (FIG. 5G). Thevacuum pump 230 lowers pressure in Boxes 25, 27. Box 25 is reduced intemperature (from 100° C. approx. to some intermediate temperature). Box27 is increased in temperature. (from ambient to the same intermediatetemperature). CO₂ and inerts are removed from the system by the vacuumpump 230. Bed 22-1, Ring B, is raised back into the ring assembly andthe assembly rotated one bed. Bed 22-2, Ring B, is then inserted intoBox 27. Box 25 (containing Bed 21-2 Ring A) is heated with atmosphericsteam to release the CO₂ and regenerate the sorbent (FIG. 5H). Thepre-heating of Box 27 then occurs as described above. The process isrepeated for all of the beds as the Decagons are rotated many times.

Design Parameters

The current basis for the design of the system is as follows:

Weight of individual monolith to be moved: 1,500-10,000 lbs. (includingsupport structure)

Approximate size of bed: Width—5-6 meters

-   -   Height—9-10 meters    -   Depth—0.15-1 meter

It should be noted that the bed dimensions could be adjusted dependingupon the particular conditions at the geographic location of each pairof systems, and the desired, or attainable, processing parameters.

For a system including 10 monoliths in each of the Decagon rings, theouter dimensions of a preferred circular/decagon structure would beabout 15-17 meters, preferably about 16.5 meters. The monolith supportstructures could be individually driven, for example by an electricmotor and drive wheel along the track, or the support structures couldbe secured to a specific location along the track and a single largemotor used to drive the track and all of the structures around theclosed loop. In either case, the regeneration box is placed at onelocation and all of the structures can stop their movement when one ofthe support structures is so placed as to be moved into the regenerationbox. The economics of a single drive motor or engine, or multiple drivemotors or engines, will depend on many factors, such as location andwhether the driving will be accomplished by an electrical motor or bysome fuel driven engine. The nature of the driving units is not itself afeature of this invention, and are all well-known to persons skilled inthe art. Examples of suitable engines include internal or externalcombustion engines or gas pressure driven engines, for example operatingusing the Stirling engine cycle, or process steam engines or hydraulicor pneumatic engines.

When a regeneration box is located above the track level, the top willbe about 20 meters above the grade of the track, and when theregeneration box is located below the grade of the track, the top of thebox will be immediately below the track grade. A box on grade will onlybe minimally above the tops of the monoliths, so as to accomodate themonolith wholly within the box during regeneration.

Where the regeneration box is not on grade, the elevator system formoving the monolith into and out of the regeneration box should be ableto accomplish the movement into and out of the box during a periodwithin the range of 30 seconds to 120 seconds, and preferably between 30and 45 seconds. The shorter the time period, the greater the flexibilityin the process parameters that are available for the process. It isrecognized that there are certain inherent mechanical limitations inmoving the massive monoliths. One advantage where the regeneration boxis on grade, is that vertical movement is not needed, as the monolithmerely rotates into the box, as part of its rotational movement, andseals; thus avoiding the vertical movement, the loss of time and theadditional capital cost of the elevators. In each case, the two edges ofthe bed are solid and form seals with the edges of the regeneration box.

Operational and Design Details

This section is divided into the following sub-sections:

-   -   Section i—Description of the overall system design and the use        of the carburetor system for energy recovery    -   Section ii—Process description including simplified PFD and        description of major items of equipment    -   Section iii—Conceptual mechanical design    -   Section iv—Issues that have to be examined in more detail to        arrive at a final optimized design

Discussion

i. CO₂ Adsorption and Removal Process

In the process of this invention, CO₂ is adsorbed from the atmosphere bypassing air, or mixtures of air and effluent gases, through a sorbentbed, suitable sorbents preferably include amines, and preferablypolyamines with at least a major proportion of the amine groups on thesorbent being primary amines. Once the CO₂ has been adsorbed by thesorbent it is stripped from the sorbent and collected, while the sorbentis regenerated. This step is performed by heating the sorbent with steamin a sealed containment, or regeneration, box. This releases the CO₂ andregenerates the sorbent. The CO₂ is collected and the sorbent is thenavailable to re-adsorb CO₂ from the atmosphere. A limiting parameter onthe process is that the sorbent can be de-activated if exposed to air attoo elevated a temperature. Thus, usually the sorbent has to be cooledbefore it is returned to contacting the air stream. This is achieved, inaccordance with the present invention, by lowering the pressure of thesystem so that the steam and water remaining in the regeneration boxafter the release of CO₂ evaporate, thus cooling the system to thesaturation temperature of the steam at its new lowered partial pressure.Furthermore, as described below, the heat released in this process isused to pre-heat a CO₂-loaded sorbent bed, so as to provideapproximately 50% sensible heat recovery, with a beneficial impact onenergy and water use. This concept is useful even if an oxygen resistantsorbent is utilized to further lengthen the effective life of thesorbent and of the monolith substrate.

Generally, a longer time is required for adsorption of CO₂ from the airby the sorbent, than is required for the release of the CO₂ in theregeneration step. With the current generation of sorbent thisdifference will require an adsorption period approximately ten timesgreater for the adsorption step compared with that required for CO₂release and sorbent regeneration. Thus a system with ten monoliths and asingle regeneration unit has been adopted as the current basis. If asorbent is operating in a system where it will have an adsorption periodonly approximately five times greater for the adsorption step comparedwith that required for CO₂ release and sorbent regeneration, the numberof monoliths required in a system, for each regeneration box, could bereduced, e.g., to one regeneration box to serve 5 monoliths. This alsodepends upon the concentration of CO₂ in the gas mixture being treated,and the desorption period for any particular sorbent.

As discussed above, the regenerated sorbent bed is preferably cooledbefore it is exposed to air so as to avoid potential de-activation bythe oxygen in the air. In accordance with this invention, this coolingis achieved by lowering the system pressure in the regeneration box,after regeneration has occurred, thus lowering the steam saturationtemperature. According to this invention, this is accomplished in a waythat a significant amount of energy removed from the regeneratedmonolith during the de-pressurization step, is transferred to a secondbed containing CO₂.loaded sorbent prior to its desorption step, thusproviding some of the energy to heat the second bed to release the CO₂and regenerate the sorbent. This heat transfer from one regeneration boxto a second reduces the operating cost of providing solely fresh steamto heat the monolith bed. The remaining heat duty for the second box isachieved by adding atmospheric steam, but less is required thus savingcosts. This process is repeated for alternate monoliths in each of thetwo boxes and improves the overall thermal efficiency of the system.This concept is shown in FIGS. 1 through 6, 1 land 12.

In the preferred embodiment as shown in these drawings, there are ten“monoliths” located in a decagon arrangement and which are located on acircular track. There are two circular/decagon assemblies associatedwith each process unit and they interact with each other (see FIG. 1 andFIGS. 5A-5H). Air is passed through the monoliths by induced draft fanspreferably located opposite the radially inner surfaces of themonoliths. At one location the monoliths are adjacent to a box intowhich the monoliths are inserted, as shown by vertically moving the bedout from the track, for processing (i.e. where they are heated withsteam to release the CO₂ from the sorbent and regenerate the sorbent).Alternatively, the box can be on grade, so that the monolith merelymoves along the track into the regeneration box 1 or moves outwardlyfrom the track, into a box, and on grade. The latter method reduces theenergy used in moving the bed, while allowing the two regeneration boxesto be located adjacent, closer to each other.

The basic operational steps for the systems of FIGS. 1-4 and 11-12 asdefined above would thus be:

-   -   1. Bed 21-1 (Ring A) after making one full rotation, is rotated        into position and then moved, e.g., vertically into the Box 25        for processing, FIGS. 1-4 and 5.    -   2. Box 25 (containing Bed 21-1 (Ring A)) is heated with steam at        atmospheric pressure and CO₂ generated is removed, FIG. 5A-H.    -   3. Bed 22-1 (Ring B) is placed in Box 27 while Box 25 is being        processed to regenerate the sorbent.    -   4. The steam supply to Box 25 is stopped and the outlet piping        for the CO₂ and condensate isolated. Box 25 and Box 27 are        connected by opening valves in connecting piping 125.    -   5. The pressure in Box 27 is lowered using a vacuum pump 330        associated with Box 27. This lowers the system pressure in both        boxes and draws the steam and inerts remaining in the        regenerated Box 25 into the other Box 27 and then to the vacuum        pump 330. This cools the regenerated Box 25 (and thus Bed 21-1        Ring A) to a lower temperature (i.e. the saturation temperature        at the partial pressure of the steam in the box) and reduces the        potential for oxygen deactivation of the sorbent when it is        placed back in the air stream. This process also heats Box 27        (and thus Bed 22-1 Ring B) from its temperature after adsorption        up to the saturation temperature at the partial pressure of the        steam in the box 27. Thus energy has been recovered from the        regenerated Box 25, and the amount of atmospheric pressure steam        required to heat Box 27 (and thus Bed 22-1 Ring B) is reduced.    -   6. The valve 125 between the two Boxes 25, 27 is closed and the        boxes isolated from each other. Bed 21-1, Ring A is now cooled        below the temperature where oxygen deactivation of the sorbent        is of concern when the bed is placed back in the air stream. The        second Box 27 and Bed 22-1 Ring B have been preheated and thus        the amount of steam required for heating the Box and Bed is        reduced.    -   7. Bed 21-1 Ring A is then vertically moved back onto the        Decagon track assembly. Box 27 is heated with atmospheric steam        and the CO₂ is collected. The Ring A bed assembly is rotated by        one bed and Bed 21-2 Ring A is then inserted into the        regeneration Box 25, where it is ready for preheating. FIG. 5H.    -   8. When Box 27 (containing Bed 22-1 Ring B) has been fully        regenerated the steam supply to Box 27 is isolated and the        piping 337 for the CO₂ and condensate is closed using valves.        The valving between the Box 25 and the regenerated Box 27 is        opened and the pressure in Boxes 27, 25 is reduced using the        vacuum pump 230 for Box 25. The temperature of Box 27 (and thus        Bed 22-1 Ring B) is reduced (see 5 above). The temperature of        Box 25 (containing Bed 21-2 Ring A) is increased (see 5 above).    -   9. Bed 22-1 Ring B is raised back into the bed assembly and the        assembly rotated one bed. Bed 22-2 Ring B is then inserted into        Box 27. Box 25 (containing Bed 21-2 Ring A) is heated with        atmospheric steam to release the CO₂ and regenerate the sorbent.

It is understood that reference to a “bed” includes both a monolithicsubstrate as well as an enclosed particulate bed held within the samesize volume.

This process is repeated continually and the two ring track assembliesoperate together, although the monoliths for each decagon are moved inand out of their boxes at slightly different times, so that the heatfrom cooling the earlier regenerated box preheats the later box when thelater monolith is in place.

In FIGS. 1 and 2 the boxes are placed above the rotating bed assemblies(which are located at nominal grade) and the monoliths are moved up intothe boxes. The only elevated structure is that required for the boxes,which are located above the rotating monoliths on a cantileveredstructure.

In FIGS. 3 and 4 the boxes are located below grade and under therotating bed assemblies. The boxes would be located in a singleexcavation with adequate access for maintenance and process piping.

In FIGS. 11 and 12, the boxes are located on grade, preferably over thetrack so that no additional vertical movement at the machinery isnecessary. Alternatively, the regeneration box on grade can be locatedoutwardly from the Decagons, and moved radially from the track.

In either case ancillary equipment (such as pumps, control systems,etc.—see section 2) would be located at grade radially inside of therotating bed assemblies.

ii. Process Equipment and Controls

FIG. 6 shows the general design from the proposed system:

-   -   There are two decagons of monoliths in a single system. Thus a        single system contains 20 (twenty) monoliths.    -   There are nine fan installations for each decagon (there is no        set of fans at the location where the monoliths are inserted        into the boxes). At present it is preferred that there will be        two vertically arranged axial fans associated with each bed of        the size described above, i.e., a height of 10 meters and a        width of 5 meters. Thus for a single system there will be        2×18=36 axial fans. However, the selection of the number and        size of fans depends upon many factors.    -   The nine fans per decagon each remain stationary (i.e. they will        not rotate with the beds). Preferably a sealing system such as        walls with a flexible end seal is provided with each fan, to        minimize bypassing of the air around the monoliths. It is        understood that the monoliths do not move continuously, but        rather stop as one bed reaches the regeneration box location,        and then restarts as that bed leaves the regeneration box. The        stationary fans are located so that when a bed enters a        regeneration box, each bed is located opposite to and sealed        with a fan installation. Alternatively, the fans can be attached        to the rotating bed structure and be fixed with the beds. In        that case the number of fans would increase to 2×20=40 axial        fans per single system. (See Section 3).    -   There are two regeneration boxes 25, 27 in a single double track        ring system; each box serves one of the decagons.    -   The size of the monoliths is not standardized. As an initial        estimate it should be assumed that each bed is 5 meters wide×10        meters tall by 1 meter deep. This initial size can be modified        based upon economic analysis and other factors.    -   Only the major valving is shown in FIG. 6 and additional        valving, instrumentation, piping and controls are required for        safe commercial operation, which are well known to the art.

During regeneration and CO₂ release from a bed, steam at atmosphericpressure and a temperature of 100° C.-120° C. is supplied directly tothe regeneration Box 25, 27 containing the bed. The effect of the steamis to heat the bed and the box and release CO₂ and produce condensate.The condensate is removed to a collection system. The CO₂ is removedfrom the box, together with some steam and inerts, by the action of theCO₂ Blower 225, 227. The exhaust stream from the box is passed through aheat exchanger (condenser) 240 where the stream is cooled and furthercondensate is produced, which is sent to the condensate collectionsystem 291. Finally the product CO₂ is sent via line 229 to storage andcompression or can be used directly in another process, such as algaegrowth, without compression. The compression of the CO₂ is not includedin the scope of this process description. Preferably, the air is atleast partially withdrawn from the regeneration box 25, 27, after it issealed with the bed, before the steam flow is started, especially wherethe CO₂ is to be compressed. Preferably, the pressure in the sealedregeneration box is reduced to not greater than 0.2 BarA before feedingthe steam and stripping the CO₂. It is preferred that as much of thenon-condensibles from air be removed as feasible, in order to reduce thecost of compression.

It is desirable to reduce the amount of water in the CO₂ exhaust streamafter the condenser, as the more water present the higher will be thecompression costs associated with storing the CO₂ product; morecondensate will have to be removed in the inter-stage coolers of thecompressors if not removed upstream. The amount of steam left in theexhaust stream sent to storage will be a function of the lowesttemperature of coolant that is available and the size of the condenserthat is installed. Determination of these values in any particular caseis based upon an economic assessment of the relative costs ofcompression (capital and operating), coolant temperature (e.g. whetherto use ambient air, cooling water or a refrigerant) and capital cost ofthe heat exchanger.

If correctly designed, the condenser should also be able to separate theliquid and vapor streams. However, a knock-out drum or similar type unitmay be required to separate the liquid and vapor streams before thevapor stream is passed to the CO₂ Blower 225, 227.

The CO₂ Blower 225, 227 could be a liquid ring pump. If that type ofunit is selected then it will be able to handle liquid condensate in theincoming feed and the condensate will be eliminated from the liquid ringsystem and sent to condensate storage. If a liquid ring type pump unitis not used then additional steps may be required to ensure that thevapor stream entering the blower does not contain a significant amountof liquid. Therefore, the selection of the type of unit used for the CO₂Blower may have an impact on the design of the upstream equipment.

When the regeneration step is completed, all valving is closed and thusboth boxes are isolated. In order to next cool the box and bed that havejust finished the CO₂ release and sorbent regeneration step and pre-heatthe other box and bed, which are at ambient temperature the followingsteps occur:

-   -   The isolation valve 126 between the boxes is opened    -   The vacuum pump 230, 330 associated with the bed at ambient        conditions is turned on    -   The effect of the vacuum pump is to draw the steam (initially        at, e.g., atmospheric pressure and approximately 100° C.) from        the box that has finished CO₂ production and bed regeneration        (the “hot” box), into the box at ambient temperature. The lower        pressure will cool the hot regenerated box and regenerated bed        to a temperature substantially below the initial temperature        after regeneration, i.e., approximately 100° C., due to the        reduction in partial pressure of the steam which reduces the        saturation temperature of the steam. As the vapor and steam are        drawn from the “hot” box and bed this stream will start to heat        the second box and bed (initially at ambient temperature) due to        condensation of the steam on the walls of the box and inside the        channels of the sorbent bed. As the vacuum pump operation        continues, the pressure in both boxes decreases and reaches a        final pressure (approximately 0.2 Bar A in the current example).        At this point both boxes and their monoliths will be at        approximately the same temperature (approximately 60° C. in the        currently example). Thus the “hot” bed has been cooled to a        temperature where, when it is returned to the air stream for        further CO₂ adsorption, the sorbent will not be deactivated to        any significant extent by the presence of oxygen in the air.        Simultaneously, the bed at ambient temperature has been provided        with a significant proportion of the heat needed to raise its        temperature to approximately 100° C. for the CO₂ stripping from,        and regeneration of, the sorbent. The final pressure to which        the combined boxes will be brought is determined by the        temperature restrictions on the sorbent in the presence of        oxygen.    -   Once the defined pressure level in both boxes 25, 27 is reached        the vacuum pump 230, 330 is stopped, the isolation valve 126        between the boxes is closed and the regeneration bed is returned        to atmospheric pressure.    -   The cooled bed is returned to the ring track assembly, which        assembly rotates until the next bed is moved into position to        enter the box, and the rotation then stops.    -   The second box and bed in the second box 25, 27 that were        pre-heated to approximately 60° C., is in the meantime supplied        with atmospheric pressure steam and heated to 100° C. for CO₂        removal and sorbent regeneration. The CO₂, steam and inerts are        removed by the CO₂ Vacuum Blower 225, 227 associated with that        Box. (See text above and FIG. 6).    -   The process is then repeated continually, to alternatingly        regenerate Boxes 25, 27.

It is possible that only a single CO₂ Blower and a single CO₂ VacuumPump could be used for each pair of regeneration boxes, a separateblower and pump for each box, or a central system, i.e. a single CO₂Vacuum Pump 230, 330 and a single CO₂ Blower 225, 227 could be used toserve multiple system pairs.

FIGS. 1 and 2 show the conceptual mechanical design where there are twodecagons in each system and where the beds are raised into or from theboxes which are located above the circular track system and supported bya cantilevered structural steel structure. FIGS. 3 and 4 show a similarconcept except that the boxes are located below grade in a singleexcavation and the boxes are lowered into the boxes. It is also feasibleto have the box on grade, and merely rotate each bed into a sealedrelationship with the box, as the ring rotates and then stops when thebed is sealed in the regeneration box.

FIG. 7A shows the conceptual design of the fan support system for theinduced draft axial fans. Vertical walls 38 extending from each edge ofthe beds to a location radially inwardly of the fans (only one such wallis shown in FIG. 7A) along with a surface seal 136 where the wallscontact the edge of the beds, plus top and bottom surfaces 36, 37 shownin cross-section, extending between the vertical walls, will prevent airfrom bypassing around the beds 21, 22, with the fans 26 remaining in afixed position. Preferably, each of the walls 38 and top 36 and bottom37 surfaces are provided with an elastomer bumper 136 that would notcontact the front of the bed 22 but which would press against the edgesof the bed when the bed 21 was fully rotated into the air captureposition.

FIG. 7B shows a conceptual design where the fans 326 are rotated withtheir associated monoliths 21. This would require the fan supportstructures to be part of the ring rotation system and would increase thepower required for rotating the monoliths, particularly the initialtorque required to start the rotation. This option would allow thebypassing of air around the bed to be eliminated as the seals would bepermanent and would not have to move.

FIGS. 8A, B and 9 show a conceptual arrangement of the fans 326 andplenums 425 that could be employed to ensure even distribution of theair across the monoliths using two fans per bed, when the beds are 10meters tall.

The mechanical operations that will be required of the positioningsystem to ensure that the monoliths will be moved into and out of theboxes precisely include:

-   -   Rotation of the two sets of bed assemblies around a circular        track on a support structure.    -   Precise location of the position where the monoliths are to be        stopped so as to ensure the free movement of the monoliths into        and out of the regeneration boxes, and into and out of the        sealable relationships with the air guidance walls and seals,        when the fans are stationary.    -   Removal of the bed from the bed assembly, insertion of the bed        into the regeneration box, removal of the bed from the box and        re-insertion of the bed onto the circular track assembly, where        the bed is to be vertically moved. When the regeneration box is        on grade, removal of the bed would not be necessary.

The monoliths are to be designed so that there is an air-tight sealbetween the monoliths and the internals of the box, and between the bedand the fan support structure when in the positions where air is passedthrough the bed. FIGS. 10A, 10B and 10C show conceptual designs for aside by side tapered seal system that will seal the bed in either theupper and lower regeneration box (FIG. 10A) positions of a regenerationbox (FIG. 10B). FIG. 10C depicts an elevation side view.

Two seal systems are installed side by side on each bed frame, eachmatched with a channel 150 in a regeneration box. One channel is in thebox and the other channel is in the ring assembly where the bed islocated for CO₂ removal from the air stream.

Each of the channels 150 into which the seals will pass is also tapered.When inserted upwards the seal used is narrow at the top—relative to thechannel which is wide at the bottom relative to the seal. This resultsin a tolerance for the seal to be inserted into the channel in which itwill slide and seal. The channel into which the seal slides is alsotapered to match the taper of the seal. As the bed is raised the gapbetween the channel and the seal narrows. This both gradually centersthe bed in the correct location and also gradually decreases the gapbetween the seal and the channel. When fully raised the seal and thechannel are the same width from top to bottom, the seal is tight againstthe channel, producing the seal, and the bed is located in exactly thecorrect position.

When inserted downwards, the other seal is used which is narrow at thebottom, which allows a tolerance for the seal to be inserted into thetapered channel (which is wide relative to the seal) and has the sametaper as the seal) in the lower position within which it will slide andseal. As for the seal operation in the upward direction, the gap betweenthe seal and the tapered channel will decrease as the bed moves intoposition, centering the bed and producing the required seal. Inaddition, there is also a seal focused between the bottom of the bed andthe bottom of the regeneration box above the track and the top of thebed and the top of the regeneration box when the box is below the trackas in FIGS. 3 and 4. When the regeneration box is on grade as in FIGS.11-12, the edges or sides of the bed for the seal.

When designing the elevator system for vertical movement of the bed,either up or down, the approximate time period desired for bed verticalmovement, for monoliths weighing about 10,000 lbs, and having thedimensions 5 ms×10 ms×1 m, between the track and the box—is 30 secondsto 120 seconds. The shorter this time period, the greater theflexibility in the process parameters that is available for thedevelopment of the process. It is for this reason that a regenerationbox on grade holds some advantages.

4.1 Sorbent Properties and Bed Thickness

It should be understood that the specific dimensions and other numericalparameters set out above are based upon the use of the now conventionalPolyethyleneamine (“PEA”) as the sorbent. As improved sorbents arerealized, that adsorb more quickly and/or are less susceptible to theeffects of oxygen at elevated temperatures, for example, dimensions andtemperatures of operation, as well as the number of beds perregeneration box and the speed of the beds around the track can change.

At present the pressure drop through the sorbent bed (which is usually aporous silica or alumina substrate with PEI present on its surfaces) ispreferably limited to 1 inch H₂O and, given the current structure of thesorbent bed and the superficial air velocity used for the design (2.5m/s in the free duct) results in a defined depth (in the direction ofair flow) for the bed. This, in turn, affects the depth of the box. Theassumed pressure drop, bed porosity, channel size, superficial airvelocity can all be modified with changes in the sorbent and/or thesubstrate, so that in conjunction with the sorbent performance, that canresult in a different preferred bed depth. One improved system isachieved by using a substrate formed from an alumina-coated silica witha primary amine polymer, such as a poly(allyl)amine, or one of itsderivatives, coated on its surfaces.

4.2 Minimum Design Pressure—Regeneration Boxes

The most significant effect of the minimum design pressure selected willbe on the cost of the boxes used for heating the sorbent monoliths. Theminimum design pressure is selected based upon achieving a steamsaturation temperature (at the steam partial pressure in the box at theminimum design pressure) such that the bed is cooled below thetemperature at which significant deactivation of the sorbent occurs whenit is exposed to oxygen in the air stream. The lower the pressure thethicker the plates and heavier the stiffening structures required forthe box. Utilizing a primary polyamine, such as poly(allyl)amine, as nowgenerally available, preferably the current minimum design pressure of0.2 Bar A the box is required to be a large, heavy and expensive item ofequipment even with a bed size of approximately 3 m×5 m×1 m. In acommercial unit it would be desirable to have a larger bed. However, asthe bed size is increased the weight and cost of the box will increasein a power relationship (not linearly) with the dimensions of the box.In addition, a higher minimum design pressure would allow a greateramount of heat recovery, as the “cold” box could be heated to a highertemperature and less atmospheric steam would be required. Thus, beingable to use a higher minimum design pressure (i.e. greater than 0.2 BarA) would bring significant advantages, if a sorbent is used that wouldnot be deactivated at the higher temperature.

4.3 Box Materials of Construction

When the regeneration box is constructed of carbon steel and stainlesssteel, it results in a structure that is heavy and expensive. Otherconstruction materials include, for example, carbon fiber (or otherman-made material), which would allow for savings in cost, as well as inweight.

4.4 Air Distribution Into and Out of Monoliths

It is essential that the air flow across the monoliths be as uniform aspossible. The use of induced draft axial fans with suitably designedplenums to guide the air flow are useful in this context, and are used,for example, with petro-chemical air cooler installations.

A second issue associated with the air distribution involves thevelocity of the air passing out of the circle of monoliths in thedecagon system. Depending upon the ratio of the height of the bed to itswidth, the air velocity in the plume of air rising out of the circularopening formed by the tops of the monoliths may be high, and should beconsidered in the design of the fan plenums.

4.5 Use of a Single Outlet Plenum with the Potential for Energy Recovery

It is understood that if the size of the monoliths were to be reducedthere is the potential to use a single very large axial fan installedhorizontally in the circular opening at the top of the monoliths. Thiswould draw air through the monoliths and then move all of the airvertically out of the assembly. There would be a plenum above the fan toguide the air and prevent re-circulation. In addition, the outlet plenumcould be designed to achieve some energy recovery by using a smallconstriction and then an expansion, as is done in cooling towers with asimilar fan and plenum arrangement. If the amount of air to be movedbecomes too large then this option would not be practical.

4.6 Use of Central CO₂ Blower and Condensing System and Amount ofCondensing Required Prior to CO₂ Blower

In the current design there is a condenser 240 upstream of the CO₂Blower 225. This removes water and reduces the vapor load on the blower.Alternatively, a single central condensing system can be used; thatwould process all of the CO₂ product streams from all of the units inmultiple system pairs. This would reduce the complexity of the systemsand reduce costs. However, the penalty for this would be that each CO₂Blower would have to be designed to handle a wet vapor stream with ahigher flowrate. Each system should be evaluated to determine the mosteconomic option.

4.7 Use of Central CO₂ Vacuum Pump

During the de-pressurizing of the system and transferring heat from the“hot” regeneration box to the “cold” regeneration box, a CO₂ Vacuum Pump230 is used. In the preferred design shown, a vacuum pump is associatedwith each regeneration box. Under certain circumstances one CO₂ VacuumPump can serve for both of the boxes in the two-ring system. Inaddition, a single large CO₂ Vacuum Pump serving multiple systems can beused. Reducing the number of vacuum pumps should reduce the capital costassociated with the system.

Preferably, the use of a liquid ring type pump would appear to beadvantageous as any condensate produced will be contained in the liquidring system and more readily removed.

4.8 Bed Removal/Sorbent Replacement

The sorbent monoliths will have to be serviced during the life of theprocess. This would involve maintenance activities on the bed movementsystems (both rotational and vertical), replacement of the sorbent andmaintenance, etc. These activities might be performed with the monolithsin position or they may require that the monoliths be removed from theassembly. Removal of the monoliths is achieved by installing a secondlift system which could then move the monoliths out from the track foraccess. Alternatively, the monoliths could be designed to be removedusing a crane. Other options are available.

With the foregoing disclosure in mind, it is believed that various otherways of operating multiple bed systems for removing carbon dioxide froma gaseous mixture, in accordance with the principles of thisapplication, will become apparent to those skilled in the art, includingthe use of many conventional steps and components that are or shallbecome well-known and would be useful in carrying out the presentinvention without themselves being a part of the invention. The scope ofthis invention is to be determined only in accordance with the scope ofthe following claims.

I claim:
 1. A method for removing carbon dioxide from a carbon dioxideladen gas mixture, the method comprising: providing at least two groupsof removal structures and two moving endless sloops for supporting eachof the two groups each of which move around a closed endless loop foreach group, each removal structure within each group comprising a poroussolid substrate supported on each of the removal structures, each poroussubstrate having a sorbent supported upon its surfaces, the sorbentbeing capable of adsorbing or binding to carbon dioxide; exposing eachindividual carbon dioxide removal structure to a stream of the carbondioxide laden gas mixture, during an adsorption time, to remove carbondioxide from the gas mixture, each of the removal structures supportingthe porous substrates on its respective closed endless loop being in aposition such that the sorbent is exposed to a flow of carbon dioxideladen gas mixture so as to allow for the removal of CO₂ from the gasmixture; providing a regeneration box adjacent each loop at onelocation; successively sealably placing one of the carbon dioxideremoval structures into a regeneration box at one location along each ofthe endless loop supports; exposing the sorbent on each removalstructure sealably placed within each regeneration box to process heatat a temperature of less than 130° C. during a regeneration time tostrip the CO₂ from the sorbent, such that when a removal structure issealed in place therein carbon dioxide sorbed upon the sorbent isstripped from the sorbent and captured, and the sorbent regenerated; thenumber of removal structures provided on each loop to the number ofregeneration boxes provided adjacent each loop, being directlyproportional to and directly determined by the ratio of the adsorptiontime, to the regeneration time, the adsorption time being the time toadsorb, on the sorbent, CO₂ from the gas mixture, from a base level to adesired level on the sorbent, and the regeneration time being the timeto strip the CO₂ from the sorbent, in the regeneration box, from thedesired level back to the base level, on the sorbent.
 2. The method ofclaim 1, wherein the carbon dioxide laden gas mixture is selected fromthe group consisting of ambient air and mixtures of a majority by volumeof ambient air with a minor portion by volume of a flue gas.
 3. Themethod of claim 1, wherein each of the two groups of carbon dioxideremoval structures comprises one regeneration box and between five andten removal structures.
 4. The method of claim 3, further comprisingreducing the atmospheric pressure within the sealed regeneration boxafter a removal structure is sealed within the regeneration box.
 5. Themethod of claim 4, further comprising passing process heat steam intothe regeneration box, after the atmospheric pressure in the regenerationbox has been reduced, to strip off the CO₂; and passing the stripped CO₂from the regeneration box into a CO₂ collection chamber.
 6. The methodof claim 1, wherein the regeneration box for each group of carbondioxide removal structures is located at a vertically different levelthan the endless loop structure and further comprising vertically movinga carbon dioxide removal structure into and out of a sealable positionwithin a regeneration box.
 7. The method of claim 1, wherein one of thetwo groups of carbon dioxide removal structures has an adjacent firstregeneration box and the other of the two groups of carbon dioxideremoval structures has an adjacent second regeneration box, therotational movement of each of the two groups of carbon dioxide removalstructures is off-set such that a carbon dioxide removal structureenters the second of the regeneration boxes after the regeneration of acarbon dioxide removal structure in the first regeneration box hasstarted.
 8. The method of claim 7, wherein the process heat is added tothe regeneration boxes in the form of process heat steam, and whenregeneration is ended in each of the regeneration boxes there remainssteam in that box, and further comprising reducing the atmosphericpressure in the other regeneration box to a preset pressure; opening asealed connection between the two regeneration boxes after thedesignated regeneration of the removal structure in the firstregeneration box has been completed, so as to draw out remaining steamin the first regeneration box to preheat the second regeneration box andcool down the removal structure in the first regeneration box; andremoving the cooled removal structure from the first regeneration boxback onto the endless loop, and continuing this cycle as the removalstructures move around the endless loop and cyclically reenter theregeneration box.
 9. The method of claim 1, wherein the process heat isadded to the regeneration boxes in the form of process heat steam, andthe steam entering each regeneration box is at a temperature or notgreater than about 120° C.
 10. The method of claim 8, wherein the secondregeneration box is preheated to a temperature of not greater than about60° C. and the first regeneration box is cooled to a temperature belowthat at which the sorbent would be deactivated.
 11. The method of claim1, wherein the sorbent is a primary amine polymer, and the process heatis added to the regeneration boxes in the form of process heat steam, ata temperature or not greater than about 120° C.